Isolation of virtual machine i/o in multi-disk hosts

ABSTRACT

Embodiments of the present invention relate to systems, methods, and computer storage media for concurrently maintaining a spanned virtual hard drive across two or more computer-storage media and a non-spanned virtual hard drive on one of computer-storage media. The method includes storing data of the spanned virtual hard drive across the computer-storage media utilizing volume spanning. While the spanned virtual hard drive is maintained on the computer storage media, the method includes storing data of the non-spanned virtual hard drive on one of the computer-storage media.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, and claims priority to, U.S.application Ser. No. 13/150,996, filed Jun. 1, 2011, entitled “ISOLATIONOF VIRTUAL MACHINE I/O IN MULTI-DISK HOSTS” which is herein incorporatedby reference in its entirety.

BACKGROUND

Traditionally, a host of a virtual machine provides physical disks tostore data accessible by the virtual machine. From the perspective of ahost, the data appears as a file on the disks, but from a perspective ofthe virtual machine, the data appears as being maintained in a harddrive. This file is referred to as a virtual hard drive that is eithermaintained on a particular disk of the host or the virtual hard drive isspanned across a plurality of the host disks. Because virtual machinesare implemented traditionally to leverage physical resources of a commonhost, there may be several virtual machines per host. Traditionally, ona given host, all of the virtual machines on a host are limited to anexclusive data structure configuration (e.g., all spanned or allnon-spanned). The exclusivity of a particular type of data structure mayprevent a possibility of I/O isolation variability, fault toleranceadjustments, and access adjustments.

SUMMARY

Embodiments of the present invention relate to systems, methods, andcomputer-storage media for concurrently maintaining a spanned virtualhard drive across two or more computer-storage media and a non-spannedvirtual hard drive on one of computer-storage media. The method includesstoring data of the spanned virtual hard drive across thecomputer-storage media utilizing volume spanning. While the spannedvirtual hard drive is maintained on the computer storage media, themethod includes storing data of the non-spanned virtual hard drive onone of the computer-storage media.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Illustrative embodiments of the present invention are described indetail below with reference to the attached drawing figures, which areincorporated by reference herein and wherein:

FIG. 1 depicts an exemplary computing device suitable for implementingembodiments of the present invention;

FIG. 2 depicts an exemplary node having a plurality of spanned disks, inaccordance with embodiments of the present invention;

FIG. 3 depicts an exemplary node having a plurality of discrete disks,in accordance with embodiments of the present invention;

FIG. 4 depicts an exemplary node having a plurality of disks maintainingdata in a hybrid data structure, in accordance with embodiments of thepresent invention;

FIG. 5 depicts an exemplary host having a VHD driver at a hypervisorlayer, in accordance with embodiments of the present invention;

FIG. 6 depicts an exemplary host having a VHD filter at a host filesystem layer, in accordance with embodiments of the present invention;

FIG. 7 depicts a method for concurrently maintaining a spanned hardvirtual hard drive across two or more computer-storage media (“CSM”) anda non-spanned virtual hard drive on a first CSM of the two or more CSM,in accordance with embodiments of the present invention; and

FIG. 8 depicts another method for concurrently maintaining a spannedhard virtual hard drive across two or more CSM and a non-spanned virtualhard drive on a first CSM of the two or more CSM, in accordance withembodiments of the present invention.

DETAILED DESCRIPTION

The subject matter of embodiments of the present invention is describedwith specificity herein to meet statutory requirements. However, thedescription itself is not intended to limit the scope of this patent.Rather, the inventors have contemplated that the claimed subject mattermight also be embodied in other ways, to include different steps orcombinations of steps similar to the ones described in this document, inconjunction with other present or future technologies.

Embodiments of the present invention relate to systems, methods, andcomputer-storage media for concurrently maintaining a spanned virtualhard drive across two or more computer-storage media and a non-spannedvirtual hard drive on one of computer-storage media. The method includesstoring data of the spanned virtual hard drive across thecomputer-storage media utilizing volume spanning. While the spannedvirtual hard drive is maintained on the computer storage media, themethod includes storing data of the non-spanned virtual hard drive onone of the computer-storage media.

In another aspect, the present invention provides another method forconcurrently maintaining both a spanned virtual hard drive acrossmultiple disks and a non-spanned virtual hard drive on one of the disks.The method includes receiving a first request, such as an I/O request,for data of the spanned virtual hard drive. The method also recitesdirecting the first request to the spanned virtual hard drive. Themethod also recites receiving a second request for data of thenon-spanned virtual hard drive. Further, the method recites directingthe second request to the disk maintain the non-spanned virtual harddrive. The non-spanned virtual hard drive and the spanned virtual harddrive are both accessible, at least in part, on a common diskconcurrently.

A third aspect of the present invention provides a system forconcurrently maintaining a spanned virtual hard drive across two or moredisks and a non-spanned virtual hard drive on a first disk of the two ormore disks. The system includes a host. The host is comprised of avirtual machine; a virtual hard drive driver; and a host file system.Additionally, the host is comprised of a first computer-storage mediummaintaining both of at least a portion of a spanned virtual hard driveand the entirety of a non-spanned virtual hard drive. The host is alsocomprised of a second computer storage media maintaining at least aportion of the spanned virtual hard drive and it does not maintain thenon-spanned virtual hard drive.

Having briefly described an overview of embodiments of the presentinvention, an exemplary operating environment suitable for implementingembodiments hereof is described below.

Referring to the drawings in general, and initially to FIG. 1 inparticular, an exemplary operating environment suitable for implementingembodiments of the present invention is shown and designated generallyas computing device 100. Computing device 100 is but one example of asuitable computing environment and is not intended to suggest anylimitation as to the scope of use or functionality of the invention.Neither should the computing device 100 be interpreted as having anydependency or requirement relating to any one or combination ofmodules/components illustrated.

Embodiments may be described in the general context of computer code ormachine-useable instructions, including computer-executable instructionssuch as program modules, being executed by a computer or other machine,such as a personal data assistant or other handheld device. Generally,program modules including routines, programs, objects, modules, datastructures, and the like, refer to code that performs particular tasksor implements particular abstract data types. Embodiments may bepracticed in a variety of system configurations, including hand-helddevices, consumer electronics, general-purpose computers, specialtycomputing devices, etc. Embodiments may also be practiced in distributedcomputing environments where tasks are performed by remote-processingdevices that are linked through a communications network.

With continued reference to FIG. 1, computing device 100 includes a bus110 that directly or indirectly couples the following devices: memory112, one or more processors 114, one or more presentation modules 116,input/output (I/O) ports 118, I/O modules 120, and an illustrative powersupply 122. Bus 110 represents what may be one or more busses (such asan address bus, data bus, or combination thereof). Although the variousblocks of FIG. 1 are shown with lines for the sake of clarity, inreality, delineating various modules is not so clear, andmetaphorically, the lines would more accurately be grey and fuzzy. Forexample, one may consider a presentation module such as a display deviceto be an I/O module. Also, processors have memory. The inventors hereofrecognize that such is the nature of the art, and reiterate that thediagram of FIG. 1 is merely illustrative of an exemplary computingdevice that can be used in connection with one or more embodiments.Distinction is not made between such categories as “workstation,”“server,” “laptop,” “blade,” “node,” etc., as all are contemplatedwithin the scope of FIG. 1 and reference to “computer” or “computingdevice.”

Computing device 100 typically includes a variety of computer-readablemedia. By way of example, and not limitation, computer-readable mediamay comprise Random Access Memory (RAM); Read Only Memory (ROM);Electronically Erasable Programmable Read Only Memory (EEPROM); flashmemory or other memory technologies; CDROM, digital versatile disks(DVD) or other optical or holographic media; magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or any other medium that can be used to encode desired information andbe accessed by computing device 100.

Memory 112 includes computer-storage media (“CSM”), such asnon-transitory computer-storage media, in the form of volatile and/ornonvolatile memory. The memory may be removable, non-removable, or acombination thereof. Exemplary hardware devices include solid-statememory, hard drives, optical-disc drives, etc. Computing device 100includes one or more processors that read data from various entitiessuch as memory 112 or I/O modules 120. Presentation module(s) 116present data indications to a user or other device. Exemplarypresentation modules include a display device, speaker, printing module,vibrating module, and the like. I/O ports 118 allow computing device 100to be logically coupled to other devices including I/O modules 120, someof which may be built in. Illustrative modules include a microphone,joystick, game pad, satellite dish, scanner, printer, wireless device,and the like.

FIG. 2 depicts an exemplary node 200 having a plurality of CSM, inaccordance with embodiments of the present invention. A node may be acomputing device, such as the computing device 100 of FIG. 1. Forexample, a node may be a blade, a server, or other distributed storagecomponent that is utilized for maintaining one or more portions of datathat are accessible by way of a network.

It is understood that a node, such as the node 200, may be comprised ofany number and/or type of CSM. For example, an exemplary node includesfour discrete CSM, such as four physical hard drives. In an exemplarydata storage structure, the first disk (disk 0) may be reserved for aroot operating system (“OS”), such as for the host system and/or one ormore virtual machines (“VM”). Continuing with this example, theremaining three CSM are reserved for guest container resource (e.g., avolume as perceived by a VM). This exemplary data storage structureconfiguration exposes a single volume that spans the three CSM, which isan example of volume spanning.

Spanning a volume across multiple CSM provides the appearance to a VM(or any layer at or above a hypervisor layer) that the three discreteCSM (or portions thereof) are a continuous volume. However, at the hostlevel (e.g., from the hardware perspective) there are really threediscrete CSM having multiple volumes. Therefore, the terminology usedherein may change based on the perspective from which it is viewed. Forexample, a VM may perceive a VHD while a host may perceive the same dataas a file (or volume, or partition). Additional examples will bediscussed hereinafter with respect to FIG. 4.

Returning to FIG. 2, the node 200 includes a disk A 202, a disk B 204,and a disk C 206. Each of the disks 202-206 may be any form of CSM(e.g., volatile, non-volatile, RAM, optical, hard disk, and the like).The term “disk” is used herein as a generic terminology for CSM and isnot intended to be limiting to a particular form of CSM. The disks202-204, in node 200, are disks supporting volume spanning that allowfor a volume/container to span across all of the disks. For example, avolume 1 208, a volume 2 210, a volume 3 212, and a volume 4 214 allspan disks 202-206. From a hardware perspective, the volume 1 208 isthree discrete files, a file 1 218, a file 2 220, and a file 3 222.However, from the VM perspective, the volume 1 208 is a continuousvolume maintaining a virtual hard drive (“VHD”), such as a VHD 1 216. AVHD (also referred to as a virtual hard disk) is a virtual hard diskfile format that is able to contain what is found on a physical harddisk drive (e.g., CSM), such as disk partitions and a file system. A VHDis typically used as a “hard disk” for a VM. Therefore, just like aphysical computing device may use a physical hard disk, a VM maysimilarly use a VHD.

While FIG. 2 does not explicitly depict other components (e.g.,processor, communication components, power supply, and the like) it isunderstood that such components are contemplated and are traditional toa computing device, such as that discussed with respect to FIG. 1.Therefore, FIG. 2 (and the additional figures of the presentapplication) are illustrated in a manner to convey particularinformation, but it is understood that additional components, steps, anditems may (and likely are) contemplated herein. Further, while FIG. 2depicts a stripping-type data storage configuration, it is understoodthat any volume spanning configuration is contemplated and may thereforebe utilized in connection with embodiments of the present invention. Forexample, a first volume and a second volume may utilize a firstpartition on a first CSM while the first volume and the second volumealso utilize a second partition on a second CSM. In this example, thefirst volume spans the first CSM and the second CSM while sharing acommon partition in the first CSM with the second volume. It iscontemplated that the foregoing is an example and additionalarrangements are contemplated.

FIG. 3 depicts a node 300 having a plurality of CSM, in accordance withembodiments of the present invention. The node 300 has a disk A 302, adisk B 304, and a disk C 306. However, unlike the node 200 of FIG. 2,the node 300 does not utilize spanning. Consequently, in the node 300,each VHD is confined to a discrete disk. The node 300 is comprised of aplurality of VHD's 308-328, each of which does not span multiplephysical disks.

The structure utilized in the node 200 of FIG. 2 and the structure usedin the node 300 of FIG. 3 are, however, similar in that they bothimplement an exclusive storage solution across two or more disks of thenode. In the case of FIG. 2, the two or more disks are exclusivelystructured with spanning (e.g., volume spanning). FIG. 3 provides two ormore disks that exclusively implement discrete disk utilization by a VHD(e.g., each VHD is limited to a particular physical disk). A “just abunch of disks” (“JBOD”) configuration is an example of that which isillustrated in FIG. 3.

The configuration of FIG. 2 allows for the largest possible container tobe stored. Additionally, the storage abstraction of FIG. 2 simplifiesthe allocation of container resources across the disks without activemanagement of container files on individual disks. However, theconfiguration of FIG. 2 may have shortcoming as well. If one of thethree disks (in this example) fails, the data for the entire node 200may be lost. This introduces a single point of failure at each of thedisks. This increases the likelihood of data loss by a factor of thenumber of disks used divided by the number of disks individuallyrequired to store the same data. Additionally, an exclusively spannedsolution does not provide input/output (“I/O”) isolation. For example,intensive I/O operations of a VM on the spanned disks affects theresponse time for all other VMs utilizing the same disks. Consequently,the configuration of FIG. 2 provides efficiencies in file management andcontainer size maintenance options; it also introduces fault and I/Oisolation concerns.

The configuration provided by FIG. 3 provides a higher level of I/Oisolation and fault tolerance. However, the size of a single container(e.g., portion of storage useable for a VHD) is limited to the size of aparticular disk. Therefore, when a VM needs a storage container largerthan any one single disk (or available space on a single disk), theconfiguration of FIG. 3 is ineffective.

As a result, to overcome the deficiencies of the configuration of FIG. 2and the shortcomings of the configuration of FIG. 3, a dynamic andflexible configuration is desired. FIG. 4 depicts a hybrid storageconfiguration of a node 400 having a plurality of CSM, in accordancewith embodiments of the present invention. The node 400 includes a diskA 402, a disk B 404, and a disk C 406. The storage solution provided innode 400 is not exclusively spanning nor is it exclusively discrete,instead, a combination of discrete, partial spanning, and/or completespanning of CSM may be implemented.

For example, a VHD 1 412 is a partial span of the disk A 402 and thedisk B 404 such that the VHD 1 412 resides in a container, as seen by aVM, as a volume 1 408. Similarly, a VHD 2 414, a VHD 4 418, a VHD 5 420,a VHD 6 422, and a VHD 7 424 are examples of a discrete storagesolution, where the container in which each of these VHDs is containedis limited to a discrete physical disk. Further yet, a containercontaining a VHD 3 416 spans all of the accessible disks of the node400, which is perceived by a VM as a volume 2 410.

The volume 1 408 spans two or more CSM without spanning all of the CSMwithin the node 400. The volume 2 410 spans all of the disks of the node400. Therefore, in FIG. 4, an exemplary embodiment allows for previouslyexclusive storage solutions to coexist in a common node, which allowsfor the runtime or dynamic shifting from spanned to non-spanned for anyof the resources used by a VM regardless of VM utilization criteria. Aswill be discussed hereinafter with respect to FIGS. 5 and 6, this ispossible, at least in part for this exemplary embodiment, through theuse of a VHD driver at a hypervisor layer and/or a VHD filter at a hostfile system layer.

In an exemplary embodiment, it is contemplated that a containercontaining resources for a VM expands based on need. Therefore, as theresources required increase, a container may be dynamically switchedfrom a discrete container (e.g., VHD 2 414) to a partially spannedcontainer (e.g., volume 1 408). Again, when the resources required growsbeyond an additional threshold (e.g., available space on the currentlyused CSM, I/O request, etc.), the partially spanned container may thenspan additional disks (e.g., volume 2 410). Conversely, if the resourcesrequired by a VM diminish, the container may contract from a spanned orpartially spanned container to a discrete container. Further, it iscontemplated that at least one disk of a node is exclusively a discretecontainer, while two or more other disks of the node maintain spannedand/or partially spanned containers. Further, it is contemplated that alocation (e.g., physical disk) onto which a container is maintained (forstorage and access) is selectable by a client, a user, a hypervisor,and/or a hosts file system. The ability to select the allocation ofcontainers (e.g., quantity, type, size) to one or more disks allows fora variety of optimizations to be discussed hereinafter. It iscontemplated that any combination of containers, volumes, and/or VHDsmay be implemented in embodiments of the present invention.

Returning to FIG. 4, depending on a perspective taken when discussingdifferent portions/objects, they may be referred to by different names.For example, the VHD 2 414 may appear as a discrete file from the hostlevel, but as hard disk (i.e., VHD) from the perspective of a VM. Thevolume 1 408 may be referred to as multiple spanned files from the hostlevel, but as a VHD from the VM level. Therefore, in some embodiments,it may be helpful to refer to a portion of storage in a non-descriptmanner, such as a container.

FIG. 5 depicts an exemplary host 500, in accordance with embodiments ofthe present invention. A host in an exemplary embodiment is a computingdevice, such as the computing device 100 of FIG. 1. The term ‘host’ isused as the host hosts one or more ‘guests,’ which may include VMs. Forexample, the host 500 may support the operations of a virtual machine502. Further, the host 500 may support additional virtual machines, suchas a virtual machine N 504. A guest, such as a VM, utilizes resources ofthe host. For example, a VM may be a virtualized computing system thatis embodied in the physical space of the host, leverages the host'sresources, but appears to be independent of the host to an outsideclient. Therefore, a VM, in an exemplary embodiment, is a softwareimplementation of a computing device that executes programs like aphysical machine.

The VM 502 is comprised of a VM file system 506, a disk driver 508, anda disk A 510. The VM file system 506 is an operating system operating ina virtual environment. The disk driver 508 interface with VHDs, such asthe disk A 510. However, the disk A 510 is merely a virtualized diskthat actually is relying on CSM resources of the host 500, such as adisk 1 520 and a disk Y 522. The VM 502 perceives that the disk A 510 isa resident CSM, while in actuality it is a VHD being maintained by oneor more CSM of the host.

A hypervisor layer 512 is an interface layer above a host file system516 that supports VM access to resources of the underlying host. Thehypervisor layer may support multiple virtual machines accessing commonresource of the host. A VHD driver 514 will be discussed in detailhereinafter.

The host file system 516 is an OS layer for the host 500. The host filesystem 516 controls the physical components, connections, and processesof the host 500. In an exemplary embodiment to be discussed with respectto FIG. 6, the host file system may be comprised of a VHD filter.

A host disk driver 518 is a disk driver for the host 500 that allows forthe interface of the host file system 516 and one or more CSM, such asthe disk 1 520. In an exemplary embodiment, the host disk driver is acomputing program that allows for a higher layer (e.g., host file system516) to interact with one or more disks.

The disk 1 520 is an exemplary CSM of the host 500. In an exemplaryembodiment, the disk 1 520 is one of four disks within the host 500. Thedisk 1 520, in this exemplary embodiment, maintains a file that isperceived by the VM 502 as a hard drive, a VHD A 524. Similarly, thedisk Y 522 also contains a file that is perceived by a VM as a VHD X526. While FIG. 5 depicts discrete VHDs (e.g., containers), it iscontemplated that one or more spanned (or partially spanned) containermay also be incorporated in a hybrid or an exclusive manner into thedisk 1 520 and/or the disk Y 522.

It should be understood that FIG. 5 s and other arrangements describedherein are set forth only as examples. Other arrangements and elements(e.g., machines, interfaces, functions, orders, and grouping offunctions, layers, levels, drivers, Oss, VMs, CSM, etc.) can be used inaddition to or instead of those shown, and some elements may be omittedaltogether. Further many of the elements described herein are functionalentities that may be implemented as discrete or distributed componentsor in conjunction with other components, and in any suitable combinationand location. Various functions described herein as being performed byone or more entities may be carried out by hardware, firmware, and/orsoftware. For instance, various functions may be carried out by aprocessor executing instructions stored in memory.

The components may communicate with each other via a network, which mayinclude, without limitation, one or more local area networks (LANs)and/or wide area networks (WANs). Such networking environments arecommonplace in offices, enterprise-wide computer networks, intranets,and the Internet. It should be understood that any number of hosts,servers, VMs, and CSM may be employed within a system within the scopeof the present invention. Additionally other component not shown mayalso be included within the system.

Returning to FIG. 5, which illustrates the VM 502 communicating an I/Orequest to access data maintained on a CSM of the host 500. The I/Orequest is communicated from the VM 502 and received at the hypervisorlayer 512. The I/O request is intercepted at the hypervisor layer 512 bythe VHD driver 514.

The VHD driver 514 is a program that intercepts I/O requests to identifystorage options. The storage options may include determining whererequested data is stored (e.g., what container, what CSM of the host,what directory, etc.). The storage option may include determining wheredata should be stored (e.g., what container, what CSM of the host, whatdirectory, etc.). The storage option may include determining how thedata is stored (e.g., spanned, partially spanned, discrete). The storageoption may include determining if the data should migrate (e.g.,optimization of I/Os hitting a particular CSM, expansion of a container,contraction of a container, etc.).

In order to accomplish the functionality of the VHD driver 514, ametafile may be maintained for a VM. For example, a metafile maymaintain an index of data storage locations, options, VHD type, andmetrics associated with data access size, frequency, and the like. Themetafile may be used by the VHD driver 514 to determine where particulardata is stored, how it is stored, and if optimizations may be performed.Optimizations may include, for example, moving containers from one CSMto one or more other CSM to reduce I/Os to one or more CSM. Otheroptimizations may include reducing fault impact by reducing the numberof containers residing on a particular CSM. Other optimizations mayinclude reducing the number of CSM spanned by a container when the samesized container may be maintained on fewer CSM. Other optimizations arecontemplated.

The metafile may be maintained in a particular location of a host foreasy and efficient access. For example, the metafile may be maintainedin a particular container of a particular CSM (e.g., first sector ofdisk 0). In the alternative, the metafile may be maintained at alocation that is identified in a header or other portion of an I/Orequest, such that upon interpreting the I/O request, the location of arelated metafile may be determined.

The VHD driver 514, in an exemplary embodiment, allows for the dynamicadjustment of storage structures in a runtime environment. For example,the process of intercepting I/O requests at the hypervisor layer 512allows for the host 500 to dynamically adjust how data is stored on thedisk 1 520 and the disk Y 522. This dynamic adjustment allows fordiscrete containers to reside on the same CSM as spanned container. Thedynamic adjustment also allows for discrete containers (e.g.,non-spanned VHD) to transition to a spanned container in a runtimeenvironment. Advantageously, the VM 502 is allowed to process dataconcurrently while a container transitions from a spanned to anon-spanned state (or vice versa). Further, by allowing for the runtimeallocation of storage, the CSM may be optimized in a host withoutreconfiguring the entire host. Consequently, utilization of the VHDdriver 514 allows for I/O packets to be directed from the VM 502 to anappropriate CSM.

In this exemplary embodiment of FIG. 5, the I/O request is then directedthrough the host file system 516 and the host disk driver 518 to the VHDA 524 of the disk 1 520 based on the direction provided by the VHDdriver 514. Had the I/O request been associated with data maintained atthe VHD X 526, the VHD driver 514 could intercept that I/O request andredirect the I/O request to the disk Y 522.

FIG. 6 provides a host 600, in accordance with embodiments of thepresent invention. The various layers, driver, machines, CSM, and thelike of the host 600 are comparable, in an exemplary embodiment, tosimilarly named items previously discussed with respect to the host 500of FIG. 5. For example, the host 600 is comprised of a VM 602, a VM filesystem, 606, disk drivers 608, VM disk A 610, a virtual machine N 604, ahypervisor layer 612, a host file system 616, a VHD filter 617, a hostdisk driver 618, a disk 1 620, a disk Y 622, a VHD A 624, and a VHD X626. As a result, those details discussed with respect to similarlynamed items of FIG. 5 will not be repeated with respect to FIG. 6.However, unlike the host 500 of FIG. 5, the host file system 616 iscomprised of a VHD filter 617.

In an exemplary embodiment, the VHD filter 617 performs functionssimilar to those discussed hereinabove with respect to the VHD driver514 of FIG. 5. However, instead of intercepting I/O packets at thehypervisor layer, the VHD filter instead intercepts I/O requests at thehost file system 616. Consequently, the VHD filter 617 intercepts theI/O packets that are passed along from the hypervisor layer 612 insteadof directly from the VMs, as was discussed with FIG. 5.

The VHD filter 617 also may access a metafile to identify informationassociated with the intercepted I/O packet. For example, the informationassociated with the intercepted I/O packet as identified from themetadata file may include a location, a CSM, a container, or the like atwhich the data correlated to the intercepted I/O is found. Additionalinformation may include frequency of access for the data, a CSM, acontainer, or a VM to aid in making optimization determinations.

Once a packet is intercepted by the VHD filter 617, the packet isdirected by the VHD filter 617 to an appropriate CSM, such as disk 1620, in this example. It is contemplated that the VHD filter 617 is ableto identify a location to which data for a VM is maintained, identifyone or more containers to which the data is to be stored or accessedfrom, determine if a container is to be spanned or non-spanned,determine if one or more CSMs are more appropriate for maintaining atleast a portion of the data (e.g., based on fault tolerance, I/Oisolation, access time, and the like).

In an exemplary embodiment, it is advantageous to implement a VHD driveroperating at a hypervisor to intercept I/O packets. For example, onlythose I/O packets originating from or destined to a VM pass through ahypervisor layer. Therefore, only those I/O packets are inspected orintercepted. This is opposed to a VHD filter intercepting I/O packets ina host file system, which may intercept I/O packets from (or to)components/applications other than a VM. In another exemplaryembodiment, it is advantageous to implement a VHD filter to interceptI/O packet. For example, the V/HD filter may be incorporated within anOS that is regularly updated, allowing for the VHD filter to be moreeasily updated. Additional advantages are contemplated.

FIG. 7 depicts a block diagram of a method 700 for concurrentlymaintaining a spanned hard virtual hard drive across two or more CSM anda non-spanned virtual hard drive on a first CSM of the two or more CSM,in accordance with embodiments of the present invention. A block 702represents a step of storing data of the spanned VHD across two CSM. Forexample, the volume 1 408 of FIG. 4 spans the disk A 402 and the disk B404, also of FIG. 4. The volume 1 408 is a container maintaining the VHD1 412, which consequently spans the two disks. The data stored in aspanned VHD may be data of a VM utilizing the resources of the two (ormore) CSM.

A VHD driver of a hypervisor layer may be responsible for storing andaccessing data in the two or more CSM. In the alternative (or incombination), a VHD filter in a host file system may be responsible forstoring and accessing data in the two or more CSM. In this exemplaryembodiment, the two or more CSM are collocated in a common machine(e.g., server, blade, computing device). Also, in an exemplaryembodiment, the two or more CSM that traditionally maintain data in anexclusive structure format (e.g., all spanned, all discrete), but areable, as a result of either a VHD driver or a VHD filter, to maintain ahybrid structure format.

At a block 704, data of a non-spanned VHD is stored on a first CSM ofthe two or more CSM from the block 702. In an exemplary embodiment, thedata of the spanned VHD and the data of the non-spanned VHD arecollocated, at least in part, on a common CSM concurrently. As a result,data of the spanned VHD and data of the non-spanned VHD are accessiblefrom a common VHD substantially simultaneously. The term “substantiallysimultaneously” may account for a limitation of CSM, which may allow foronly a single portion of data to be accessed/stored at any given time,but immediately after that read/write another portion of data may thenbe accessed, for example. The block 702 and the block 704, in anexemplary embodiment may allow for the VHD 1 412 and the VHD 2 414 ofFIG. 4 to be maintained on the disk A 402.

At a block 706 an I/O request (e.g., a packet) is intercepted. Aspreviously discussed either (or both) a VHD driver or a VHD filter maybe implemented to intercept the I/O request.

At a block 708 the intercepted I/O request is directed to an appropriateCSM. For example, a VHD driver or a VHD filter may repackage the I/Orequest to specifically identify a container, a VHD, of a CSM to whichthe I/O request content is to be directed. Similarly, the VHD driverand/or the VHD filter may alter an intercepted I/O request to direct thecontents of the I/O request to an appropriate CSM, container, VHD, andthe like. The VHD driver or the VHD filter may inspect the I/O requestto determine a desired VHD destination. Inspecting is a process ofidentifying information associated with a packet for use in making alater determination. For example, information identified during aninspection may be used to locate a metafile or information within ametafile.

It is contemplated that the non-spanned VHD to which data was stored atthe block 704 may dynamically be altered to allow for the non-spannedVHD to span two or more CSM. The ability to dynamically alter thestorage structure of a container in runtime allows a greater degree offlexibility than previously recognized by static configurations.Similarly, it is contemplated that a spanned VHD may also be dynamicallyaltered during runtime (or at any point) to become a discrete container(e.g., discrete non-spanning volume, a discrete file, etc.) on adiscrete CSM (e.g., on a particular platen of a hard disk, on aparticular hard disk, etc).

FIG. 8 depicts a block diagram of a method 800 for concurrentlymaintaining a spanned hard virtual hard drive across two or more CSM anda non-spanned virtual hard drive on a first CSM of the two or more CSM,in accordance with embodiments of the present invention. A block 802provides a first request being received for data of a spanned VHD. In anexemplary embodiment, the first request is received at a hypervisorlayer or at a host file system layer. The request may be an I/O requestfrom a VM residing above the hypervisor layer and the host file systemlayer.

At a block 804 the received first request is directed to a spanned VHDthat is spanning two or more CSM. For example, the first request may bean I/O request from a VM machine attempting to access data stored in aVHD. The VM may not be aware that the VHD to which it is trying toaccess is spanned across two or more CSM. Further, the VM may not evenbe aware of where the VHD is maintained. Consequently, a VHD driver or aVHD filter may identify those attributes (e.g., where the requested datais stored and how to access the data). At a block 806 a second requestis received for data of a non-spanned VHD. The second request may bereceived by a VHD driver or a VHD filter intercepting an I/O packet.

At a block 808, the second request is directed to a first CSM of the twoor more CSM. A VHD driver or a VHD filter may direct or cause the secondrequest to be directed to the first CSM. In an exemplary embodiment, thespanned VHD and the non-spanned VHD to which the first and secondrequests respectively are direct are maintained, at least in part, on acommon CSM.

At a block 810, a third request for data of a third VHD is received. Forexample, a VHD driver or a VHD filter may intercept an I/O packet toreceive the third request. The receiving entity may then determine acontainer (e.g., a volume) containing the third VHD is insufficient. Aninsufficient container may be a container that does not have sufficientspace for additional data to be stored. An insufficient container may beone that does not meet a determined threshold of I/Os per unit of time.An insufficient container may be one that does not provide a thresholdlevel of fault tolerance. This determination may be performed by a VHDdriver, a VHD filter, an OS, a hypervisor, and/or any combination.

At a block 814, in response to determining the container maintaining thethird VHD is insufficient, the third VHD is spanned across the first CSMand at least one additional CSM of a common node. As a result, the firstCSM, in an exemplary embodiment, maintains at least a portion of aspanned VHD, a non-spanned VHD, and at least a portion of a dynamicallyaltered VHD that spans at least one other CSM.

Additional advantages provided herein include an ability to identify VMsand/or VHDs affected by failure of one or more CSM. For example, in atraditional RAID-0 type configuration it was known that all VMsutilizing any of the CSM in a node would be affected if even one of theCSM failed. Similarly, in a static JPOD structure if a CSM is to fail,it was known which VM may have been utilizing the failed CSM. However,in a dynamically adaptable structure that allows spanned, partiallyspanned, and non-spanned containers to exist, it may be difficult toidentify which VMs are affected by a failed CSM. The metafile may beaccessed by an OS, a driver, a hypervisor, or any othercomponents/process to identify those VMs that may maintain data on theaffected CSM.

Many different arrangements of the various components depicted, as wellas components not shown, are possible without departing from the spiritand scope of the present invention. Embodiments of the present inventionhave been described with the intent to be illustrative rather thanrestrictive. Alternative embodiments will become apparent to thoseskilled in the art that do not depart from its scope. A skilled artisanmay develop alternative means of implementing the aforementionedimprovements without departing from the scope of the present invention.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations and are contemplated within the scope of the claims. Notall steps listed in the various figures need be carried out in thespecific order described.

The invention claimed is:
 1. A method in a computing environmentutilizing a processor and memory for concurrently maintaining 1) aspanned virtual hard drive across two or more computer-storage media(“CSM”) and 2) a non-spanned virtual hard drive on a first CSM of thetwo or more CSM, the method comprising: storing data of the spannedvirtual hard drive across the two or more CSM utilizing volume spanning;and while the spanned virtual hard drive is maintained on the two ormore CSM, storing data of the non-spanned virtual hard drive on thefirst CSM, wherein the non-spanned virtual hard drive does not span thetwo or more CSM.
 2. The method of claim 1 further comprising inspectingan incoming Input/Output (“I/O”) request in a hypervisor layer toidentify which CSM of the two or more CSM maintain data associated withthe I/O request.
 3. The method of claim 1 further comprising inspectingan incoming Input/Output (“I/O”) request in a host file system toidentify which CSM of the two or more CSM maintain data associated withthe I/O request.
 4. The method of claim 1 further comprising spanningthe non-spanned virtual hard drive (“spanned non-spanned virtual harddrive”) across the two or more CSM.
 5. The method of claim 4, whereinthe spanned virtual hard drive spans across at least one additional CSMthan the spanned non-spanned virtual hard drive.
 6. The method of claim1, wherein the two or more CSM are incorporated within a common node. 7.The method of claim 1, wherein the non-spanned virtual hard drive isaccessible from a discrete volume on a discrete CSM.
 8. The method ofclaim 1, wherein volume spanning is a container on which data is storedon more than one discrete CSM while providing functionality of a singlevolume.
 9. One or more computer-storage media having computer-executableinstructions embodied thereon, that when executed by a computing systemhaving a processor and memory, cause the computing system to perform amethod for concurrently maintaining 1) a spanned virtual hard driveacross two or more computer-storage medium (“CSM”) and 2) a non-spannedvirtual hard drive on a first CSM of the two or more CSM, the methodcomprising: receiving a first request for data of the spanned virtualhard drive; directing the first request to the spanned virtual harddrive spanning the two or more CSM; receiving a second request for dataof the non-spanned virtual hard drive; and directing the second requestto the first CSM, wherein the non-spanned virtual hard drive and thespanned virtual hard drive are both accessible, at least in part, at thefirst CSM substantially concurrently.
 10. The method of claim 9, whereinthe first request is an I/O request from a virtual machine operating ona host, such that the host controls the two or more CSM.
 11. The methodof claim 9, wherein the directing the first request is performed at ahypervisor layer of a host.
 12. The method of claim 9, wherein thedirecting the first request is performed at a host file system layer ofa host.
 13. The media of claim 9, wherein the method further comprises:receiving a third request for data of a third virtual hard drive;determining a volume containing the third virtual hard drive isinsufficient; and spanning the third virtual hard drive across two ormore CSM, wherein one of the two or more CSM the third virtual harddrive spans is the first CSM, which maintains the non-spanned virtualhard drive.
 14. The media of claim 9, wherein the method furthercomprises dynamically adding a spanned volume to the first CSM, suchthat the first CSM maintains both spanned volumes and non-spannedvolumes simultaneously.
 15. The media of claim 9, wherein the methodfurther comprises selecting a CSM from the two or more CSM onto which avolume will span, wherein the CSM is selected based on a number ofvirtual machines utilizing each of the two or more CSM.
 16. The media ofclaim 9, wherein the method further comprises selecting a CSM from thetwo or more CSM onto which a volume will span, wherein the two or moreCSM are not reconfigured to exclusively maintain spanned volumes.
 17. Asystem for concurrently maintaining 1) a spanned virtual hard driveacross two or more computer-storage medium (“CSM”) and 2) a non-spannedvirtual hard drive on a first CSM of the two or more CSM, the systemcomprising: a host, the host comprising: (1) a virtual machine; (2) avirtual hard drive driver; (3) a host file system; (4) a first CSMmaintaining both at least a portion of a spanned virtual hard drive andthe entirety of a non-spanned virtual hard drive; and (5) a second CSMmaintaining at least a portion of the spanned virtual hard drive anddoes not maintain the non-spanned virtual hard drive.
 18. The system ofclaim 17, wherein the VHD driver redirects I/O requests to the first CSMand the second CSM.
 19. The system of claim 17, wherein the host filesystem comprises a VHD filter that redirects I/O requests to the firstCSM and the second CSM.
 20. The system of claim 17, wherein the firstCSM and the second CSM dynamically adjust to include one or moreadditional spanned volumes and one or more non-spanned volumes.